I've never held a polymer banknote in my hands (Is this is subtle plea for a cash donation? Yeah, sure. Why not? But what would I do with foreign currency anyway but show it off.) but they are becoming more popular. Canada (home of the "Loonie") is next up for the change. Living only a few hundred miles from the "Great White North", I might be able to snag one next year. Everyone in Minnesota has a jar full of Canadian coins that we're stuck with - stores won't accept them (but they'll gladly provide them to you as change) - ditto for vending machines.
The World Polymer Notes blog is a good site cataloging everything that has been made to date. Usage of polymers as the base for the notes has an unusual geographic distribution, mostly below the Tropic of Cancer.